In the past three decades, there have been major technological efforts to increase the fuel efficiency of automotive vehicles. One technical trend to improve fuel efficiency has been to reduce the overall weight of the vehicle. A second trend to improve fuel efficiency has been to improve the aerodynamic design of a vehicle to lower its aerodynamic drag. Still another trend is to address the overall fuel efficiency of the engine.
Prior to 1970, the majority of production vehicles with a reciprocating piston gasoline engine had a carburetor fuel supply system in which gasoline is delivered via the engine throttle body and is therefore mixed with the incoming air. Accordingly, the amount of fuel delivered to any one cylinder is a function of the incoming air delivered to a given cylinder. Airflow into a cylinder is effected by many variables including the flow dynamics of the intake manifold and the flow dynamics of the exhaust system.
To increase fuel efficiency and to better control exhaust emissions, many vehicle manufacturers have gone to fuel injection systems, where the carburetor was replaced by a fuel injector that injected the fuel into a port or cylinder of the engine.
Vehicle emission standards have become so stringent that a vehicle designer can no longer just consider the emissions from the tailpipe. Increased scrutiny has come to hydrocarbon vapor emissions which can escape from the fuel system of the vehicle.
Most vehicles with fuel injectors have the fuel injectors connected with the fuel rail. Most fuel injectors are sealed to the fuel rail by being encircled by a sealing member which in turn seals against an outlet cup of the fuel rail. Over a process of time, sealing efficiency of the sealing member can be lost due to a change of its sealing capacity caused by an exposure to high concentration of hydrocarbons on one side of the sealing member. Accordingly after a long process of time there can be slight permeation of hydrocarbon vapor beyond the O-ring seal.
Utilization of multiple sealing members can slightly alleviate permeation problems but in due time multiple sealing members tend to realize the same problem as the permeation past one sealing member progressively permeates the next sealing members. Eventually, permeation of hydrocarbons from the connection of a fuel injector to the fuel rail occurs again.
Another attempted solution to the permeation problems has been to either solder or weld the fuel injectors to the fuel rail or to use compression type fittings utilizing metal-to-metal sealing. Both of the above noted solutions are undesirable.
From a practical standpoint, during fastening of the fuel rail to the vehicle engine it is desirable that there be a slight amount of axial play in the connection of the fuel rail with the fuel injector. Connecting the fuel rail to the fuel injector by welding or soldering and/or connecting the fuel rail to the fuel injector by compression fitting limits the opportunities of axial play of the fuel injector with the fuel rail and therefore greatly complicates assembly of the fuel rail and its connected fuel injectors with the vehicle engine.
It is desirable to provide a fuel delivery system arrangement with substantially reduced or eliminated hydrocarbon permeation caused by the connection of the fuel rail to the fuel injectors without utilizing compression fitting or welding or soldering.